to add a led
and for the attenuator pot
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for the volume attenuator I was thinking of doing like Sams mixer schematic.
Not sure if that would work on an output though.
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An attenuator pot works for Input and Output 
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Output attenuators are pretty uncommon in synth modules, and my own preference is to do any attenuation at the input. Modules intended to connect to external equipment that expects a line level are an exception. Maybe that’s what you have in mind. But especially if you plan to connect a synth module downstream, you want to keep the output impedance low. In that case if you want an attenuator on the output use a 1k pot. Otherwise when you plug it into a high input impedance module (or external device) you’ll lose signal level.
Use 100k on input attenuators, generally.
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I want to be able to put a volume pot on each output. I’m aiming for something like the Intellijel Quad VCA.
I’m also planning to add the summing output if possible. Which I hope will let me use the quad vca as a mixer of sorts maybe.
The Intellijel Quad VCA doesn’t have attenuators on either the signal inputs or the outputs. If I understand correctly the “Level” knobs are equivalent to the “bias” knobs on the dual VCA posted here. They control a DC bias added to the control voltage, so when you turn one up, the VCA gain increases.
Added: To clarify, you can add attenuators on the outputs, but that isn’t what the Intellijel has.
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Yes you can add attenuator as suggested. The bias controls only open up the vca ie mimick a cv signal so you can drone away. Yes use a small resistor for your led👍
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@analogoutput & @Unauthorised_service Thank you guys for answering my questions. It really helps!
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We learn every day with Rich
Personally, I have always added attenuator at the output of my Env and I don’t think I used 1K pots.
so a question, when the pot is fully open it lets the voltage flow as if no pot was present ?
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This is a great page, thanks @Dud and @Synthlurker
I’d love for someone to have a go at a DIY eurorack version of ElectroSmash - MXR Phase 90 Analysis. … hmmmmm
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i have a question about the schem, for me a TL061 it’s like a TL071 (1 opamp), but in schem it’s said U1a & U1b and U2a,b,c,d… ?
maybe transform it with only 2 TL074, and add the part of the stomp box adapter circuit for input & output synth level.
i’ve a lot of work at this time, but maybe one day 
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I would assume that all the op amp cells are interchangable, so 74s should be fine, right?
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If you read the page you can see they talk about different variants of the production version:
- Script Logo: using 6 single 741 op-amps by National or TI (like the current MXR CSP-026 '74 Handwired version).
- Block Logo : … first revisions include 6 single op-amps … Finally, the six single op-amps were replaced for three dual op-amps.
Absolutely you could use six singles or three duals or a quad and a dual or, as @Dud suggests, two quads to enable adding the synth level mods. And TL07x in place of TL06x should be fine.
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EFM Wildcat Slide+Glide
Fixed the old layout by showing where power rails are
Used VP2106 as substitute for 2n5460 (as those are getting rare)
Dual pot and DPDT switch are possible mods mentioned in Electromusic forum
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12dB l.e.p filter, old classic from Electromusic forum
Filter sweep could be smoother and resonance is more of a feedback loop
Still worth building as it uses only common parts and is very simple
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I don’t remember where I found this one but anyways I have succesfully built and verified it.
Upper right AD was missing connection to +V
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